1. Field of the Invention
The present invention relates to a magnetic shielding package of a non-volatile magnetic memory element. In particular, the present invention relates to a magnetic shielding package of a non-volatile magnetic memory element for suppressing the influence of an external magnetic field on the non-volatile magnetic memory element.
2. Description of the Related Art
A MRAM (Magnetoresistive Random Access Memory) that is a memory utilizing a magnetic substance is a non-volatile memory that can store a memory without any power supply from outside. Thus, it is a memory that does not require standby power, has unlimited rewriting endurance and high-speed performance, and is expected to consume a low power and increase its capacity.
However, the basic element of the MRAM stores information in the direction of spontaneous magnetization of the magnetic substance, and thus, by an irradiation with external magnetic field of about 10 to 50 [Oe] that is a reverse magnetic field intensity of the MRAM element, there is a possibility that the stored information is deleted or rewritten.
The MRAM element is generally mounted on a substrate in an electronic device. A semiconductor element, an element for communication, an ultrasmall motor, and the like are densely mounted on a substrate in addition to the MRAM element. Moreover, in the electronic device, a power supply unit, an antenna element, and the like are mounted. Therefore, a magnetic field at a relatively low frequency of about 100 to 300 [Oe] is present around the MRAM element. Thus, a magnetic field blocking shield is required to mount the MRAM.
A magnetic non-volatile memory element (or non-volatile magnetic memory element) including a magnetic field blocking shield has been proposed conventionally (Japanese Patent No. 3879566, Japanese Patent No. 3879576, WO 2011/111789, Japanese Patent Application Publication No. 2004-047656).
FIG. 13 shows a structure of the non-volatile magnetic memory element described in Japanese Patent No. 3879566. In FIG. 13, a MRAM element 11 is connected to a lead frame 13 with a wire 12 in a magnetic shielding package 10, and an encapsulation resin 14 containing a soft magnetic material encapsulates around the MRAM element 11. This magnetic shielding package 10a is connected to the substrate 20 with a lead extended from the lead frame 13.
FIG. 14 shows a structure of the magnetic non-volatile memory element described in Japanese Patent No. 3879576.
The magnetic non-volatile memory element 11 is connected to a lead frame 13 with a wire 12. The entire periphery of the MRAM element 11 is surrounded by a magnetic shield member 14 obtained by adhering the moldings that are formed using a soft magnetic material made of a soft magnetic metal or a soft magnetic alloy and magnetically continue, and thus, the MRAM element 11 is arranged in the state of being shielded magnetically. This magnetic shielding structure is a structure in which a MRAM chip is covered with a material (air) with a low magnetic permeability, and the outer periphery thereof is covered with a soft magnetic material having a high magnetic permeability. In this case, the static magnetic field/low frequency magnetic field pass through a soft magnetic material having a high magnetic permeability, and a material having a low magnetic permeability between the MRAM chip and the soft magnetic material prevent the entering of a magnetic flux to the MRAM side. Thus, a higher shielding effect on the MRAM chip can be obtained.
The magnetic device disclosed in WO 2011/111789 is provided from the viewpoint of facilitating the production process thereof and improving the magnetic-shielding performance and the magnetic device comprises a magnetic element and a magnetic shield having an opening wherein the magnetic shield comprises an upper part and a lower part which overlap each other in a shield region, and also comprises a side part which physically connects the upper part to the lower part. The magnetic element is arranged between the upper part and the lower part without getting out of the shield region.
Japanese Patent Application Publication No. 2004-047656 discloses a magnetic non-volatile memory device (MRAM device) with a magnetic shielding structure for suppressing the influence of external magnetic fields. The MRAM device has a magnetic shielding layer formed using a soft magnetic metal on the surface thereof for suppressing the penetration of magnetic flux into the device and penetration of magnetic flux into the MRAM device is suppressed. Furthermore, Japanese Patent Application Publication No. 2004-047656 describes that since a soft magnetic metal is used for forming the magnetic shielding layer, the magnetic shielding layer can be obtained with a higher permeability as compared to one made from a soft magnetic metal oxide such as a ferrite.
Note that in FIGS. 13 and 14, reference numerals are shown as in Japanese Patent No. 3879566 and Japanese Patent No. 3879576.
In the magnetic shielding structure described in Japanese Patent No. 3879566, the magnetic substance and the MRAM chip are in contact with each other. Thus, it is considered that there is an effect on the high frequency magnetic field. However, as to the static magnetic field/low frequency magnetic field, a magnetic flux is concentrated in a region of the magnetic substance, and thus, there is a possibility that the magnetic field reaching the MRAM increases.
In the magnetic shielding structure described in Japanese Patent No. 3879576, a soft magnetic material made of a metal/alloy having a high magnetic permeability, such as permalloy, is used as a shielding material, and thus, a large magnetic shielding effect can be expected, compared with the case of using an insulating soft magnetic material such as a magnetic-filler containing a resin, ferrite or the like. In this structure, it is desired that the all directions of the MRAM chip are shielded with a soft magnetic metal material. However, since the covering is performed by a metal, it is required to pay careful attention to the way of leading a wire out.